People in the past were walking on dirty or dusty roads with sandals on their feet. So, they had to wash their feet before entering a house. Usually a slave, servant, or host (Lk 7:44) would wash the feet of the guest. This did not happen when Jesus and the apostles gathered for the Passover because they had no host or servant. None of the apostles wanted to be at the service of others, not even to wash the feet of their Lord. So, they might have started the supper without the ceremonial washing of feet. Jesus might have noticed it and delayed it to teach them a lesson by making himself a humble servant of his disciples. According to Jewish practice, there was no practice of washing the feet during the Passover celebration.
Jesus, who came to serve and offer himself as a ransom for us, showed us the servant leadership in action. Let us humble ourselves like Jesus and be at the service of one another in the family, workplace, church, and society.